Long‐term results of vaccination with adjuvanted recombinant varicella zoster glycoprotein E during initial Bruton tyrosine kinase inhibitors therapy for chronic lymphocytic leukemia or lymphoplasmacytic lymphoma
Authors: Michael T. Brady, Nathan Laniewski, Myla Strawderman, Charles C. Chu, Preshetha Kanagaiah, Mark Y. Sangster, David J. Topham, Jonathan W. Friedberg, Clive S. Zent
Journal: American Journal of Hematology (2023)

Herpes zoster reactivation (VZR), commonly known as shingles, can lead to postherpetic neuralgia and other more serious complications. VZR risk increases with age and other causes of immunosuppression including chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) and lymphoplasmacytic lymphoma/Waldenstrom macroglobulinemia (LPL).1 We have previously shown that patients with CLL or LPL can have short-term immune responses to vaccination with adjuvanted recombinant VZ glycoprotein E (rVZgE; GlaxoSmithKline Biologicals) while on therapy with oral covalent-binding Bruton tyrosine kinase inhibitors (BTKi).2 We now report that these responses are sustained at 24 months post-vaccination in most patients. The study enrolled CLL and LPL patients aged ≥50 years on treatment for progressive disease with a BTKi for ≥3 months.2 The only other permitted previous therapy was rituximab completed >1-year prevaccination. Exclusions were VZR within 1 year, other vaccinations within 3 months, or prevaccination lymphocyte count >20 × 109/L to avoid interference with cellular assays. Study participants received two doses of rVZgE vaccine 8–12 weeks apart per product label with blood sampled prevaccination, 4 ± 1 week, and 24 ± 3 months after the second dose of vaccine. Humoral vaccine response analysis compared concentrations of serum IgG specific for VZgE to selected non-VZ proteins measured by ELISA as previously described.2 A positive humoral response was defined by ≥four-fold increase in VZgE-specific serum IgG compared to prevaccination. Cellular response to vaccination was measured in peripheral blood mononuclear cells stimulated with a peptide pool covering the VZ envelope gE domain using intracellular cytokine staining and flow cytometry. High-dimensional clustering analysis using FlowSOM identified five unique CD4+ T-cell clusters significantly associated with rVZgE vaccination.2 A ≥ two-fold increase in the frequency of the sum of the CD4+ T-cell clusters compared to baseline levels or irrelevant control peptide was considered a positive response. Supplementary data and Table S1 provide details of methods and statistical analysis. Thirty-two (CLL = 22, LPL = 10) patients were vaccinated between January and September 2019. Twelve CLL patients had previous rituximab (median 3.1 years prior to vaccination) in clinical trials as previously described.2 One patient died of causes unrelated to lymphoma or vaccination prior to the 24-month blood draw; samples were obtained from the other 31 patients. At the time of the 24-month blood draw 27 of 31 patients were receiving BTKi therapy, four CLL patients stopped due to treatment-related adverse events. One patient switched from ibrutinib to acalabrutinib prior to the 24-month sample to minimize side effects. No patients had VZR or progression of disease within the 24-month follow-up period. Additional patient characteristics can be found in Tables S2 and S3. Thirty of 32 patients had detectable serum VZgE-specific IgG prevaccination and all tested patients had detectable levels at 4 weeks and 24 months after vaccination (Figure 1A). Control serum levels of IgG specific for the H1 hemagglutinin of influenza were minimally changed after vaccination (data not shown). The study is registered at clinicaltrials.gov study number: NCT03771157. The primary endpoint of this study was humoral response 24 months (± 3 months) after vaccination defined by ≥four-fold increase from prevaccination levels in VZgE-specific serum IgG. Seventy-five percent of patients (90% CI, 59.4–86.9) had a humoral response to vaccination at 4 weeks. Among responding patients, 56.5% (90% CI, 37.5–74.2) had a sustained humoral response 24 months after vaccination. The overall humoral response rate for all patients at 24 months compared to prevaccination was 41.9% (90% CI, 26.9–58.2). The VZgE-specific serum IgG concentration geometric mean increased from 1.7 μg/mL (90% CI, 1.2–2.3) prevaccination by 13.2-fold (90% CI, 8.0–21.6) to 22.5 μg/mL (14.4–35.1) 4 weeks after vaccination. Compared to prevaccination the geometric mean at 24 months increased by 3.2-fold (90% CI, 2.1–5.0) to 5.6 μg/mL (90% CI, 3.6–8.6), Figure 1A, B. CLL patients treated with prior rituximab had a non-significant lower fold change in VZgE-specific IgG at 24 months compared to CLL patients not treated with rituximab (p = .06). There was no significant association between prior rituximab and achieving humoral response (p = .38) (Supplemental data Table 3). Cellular response was achieved in 81.3% of patients (90% CI, 66.4–91.5) 4 weeks after vaccination. Among those who responded, the response was sustained in 65.4% of patients (90% CI, 47.4–80.6) 24 months after vaccination. The overall cellular response rate in all patients at 24 months was 54.8% (90% CI, 38.7–70.2). The number of activated VZgE-specific CD4+ T-cells increased from a median of 86 cells (IQR, 36–185) per million CD4+ T-cells prevaccination by 4.6-fold (IQR, 2.5–8.9) to 426 cells (IQR, 136–942) per million CD4+ T-cells 4 weeks after vaccination. Compared to prevaccination the number of activated CD4+ T-cells at 24 months increased 2.2-fold (IQR, 1.0–3.8) to a median of 115 cells (IQR, 47–422) per million CD4+ T-cells (Figure 1C, D). Of the patients with a humoral response at 24 months, a cellular response was detected in 69.2% (90% CI, 42.7–88.7), while 44.4% of subjects (90% CI, 24.4–65.9) without a humoral response achieved a cellular response. A significant association was not found between humoral and cellular responses using a chi-square test (p = .17). Ten patients, 32.3%, (90% CI, 18.7–48.6) did not meet the criteria for either a humoral or cellular response 24 months after vaccination. Of these patients, 8 had CLL and 6 had previously received rituximab. Failure to achieve either a humoral or cellular response was not statistically different (Fisher's Exact Test p = .13) among those with prior rituximab (6/12, 50%) versus those without (4/19, 21%). This prospective pilot study shows that CLL and LPL patients vaccinated with rVZgE while on treatment with BTKi can maintain durable response 24 months after vaccination, with humoral response rates of 41.9% and cellular response rates of 54.8%. Among patients with a humoral response at 4 weeks, 56.5% had a sustained response 24 months later. The reduced response rate at 24 months compared to 4 weeks is expected based on previous studies reporting that healthy subjects vaccinated with rVZgE have a decrease in response rates from 97.8% humoral and 93.3% cellular 1 month after vaccination to 80% humoral and 57% cellular at 24 months.3 In a second study of patients with hematological malignancies (excluding CLL patients treated only with oral therapy) 65.4% had humoral response and 83.7% had cellular response 1 month after vaccination.4 One-year follow-up on a subset of these patients demonstrated decreased humoral response rates of 52.1% and cellular response rates of 66.7%.4 A more recent study of treatment naïve and BTKi-treated CLL patients vaccinated with rVZgE found humoral response rates to be 40% in the BTKi-treated group 3 months after vaccination.5 Prolonged humoral response was assessed in a subset of patients (both treatment naïve and BTKi-treated) and no significant difference in anti-gE levels was found at 3, 12, and 24 months after the second dose of vaccine. The difference in response rates between this study and our data could be attributed to the time of first evaluation of response at 3 months versus 4 weeks following the second dose of vaccine. Although only 12 patients were included in the 24-month analysis by Pleyer et al, antibody levels remained stable compared to 3 months suggesting a humoral response rate similar to what we observed at 24 months. Compared to 24-month vaccine responses in healthy subjects, humoral response rates in our study are decreased but cellular response rates are similar.3 Interestingly, cellular response is thought to be the primary method of protection against VZR.6 These results are similar to those in other studies showing that BTKi-treated patients have more intact cellular responses compared to humoral responses.7 Additional studies are needed to determine if cellular response correlates with protection from VZR in this population. The strengths of this study are that it was a prospective clinical trial enrolling patients receiving BTKi as initial therapy with standard administration of vaccine and collection of samples which were analyzed in a specialized vaccine research laboratory. Limitations include the small number of subjects and the inclusion of two similar but distinct B-cell malignancies. This pilot study was of limited scope given the initial concern that disease-related immunosuppression and immune effects of BTKi would prevent any vaccinal effect. Long-term immune response was measured at 24 months rather than 12 months as originally planned due to limitations of blood collection during the coronavirus pandemic. In summary, we report that patients with CLL or LPL vaccinated with rVZgE while on BTKi therapy can achieve and maintain durable humoral and T-cell responses 24 months after vaccination, albeit at rates lower than healthy individuals. These data support the routine use of rVZgE vaccination in patients with CLL and LPL and suggest that durable benefits can be achieved in patients on BTKi therapy. Additional studies will be needed to determine why only some patients respond to vaccination and if cellular response correlates with protection from VZR. We thank patients, Sharon Lewinski RN, Maureen Tremaine RN, Tania Orzol NP, Alyssa Williams, Christine Herne PhD, Michael Flannery, and Cristin Sciortino for making this study possible. The study was supported by the Cadregari Endowment Fund of the Wilmot Cancer Institute, Wilmot Biostatistics and Bioinformatics Shared Resource, Research & Academic IT, Clinical and Translational Science Institute grant (UL1TR002001). Funding for a portion of this study was provided by GSK Biologicals SA. GSK Biologicals SA was provided the opportunity to review a preliminary version of this manuscript for factual accuracy, but the authors are solely responsible for the final content and interpretation. The authors declare no conflict of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request. Data S1. Supporting information. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.